Stir up, we beseech thee, O Lord, the wills of thy faithful people; that they, plenteously bringing forth the fruit of good works, may of thee be plenteously rewarded; through Jesus Christ our Lord. Amen.
The Sunday before the first Sunday of Advent is "Stir-Up Sunday," from the first words of the collect in the Anglican service. Traditionally, this is the day the Christmas pudding is made, and then soaked in brandy or another spirit and put away to serve on Christmas Day.
More about Stir-Up Sunday, with a traditional pudding recipe.
Jamie Oliver talks about Stir-Up Sunday and Christmas puddings.
According to Catholic Culture, Stir-Up Sunday is also the First Sunday of Advent.
A Telegraph writer makes the case for home made pudding, not one purchased at the store.